The skin friction and heat transfer occurring in the laminar boundary layerwhich caused by a vertical liquid jet impinging on a continuously moving horizontal plate werestudied. Similarity solutions for shear stress a...The skin friction and heat transfer occurring in the laminar boundary layerwhich caused by a vertical liquid jet impinging on a continuously moving horizontal plate werestudied. Similarity solutions for shear stress and heat distribution were obtained by using thehooting technique. The results show that the skin friction decreases with an increase of velocityparameter, the evolving of thermal boundary decrease with increasing in Prandtl number, but increasewith increasing of velocity parameter.展开更多
The problem of momentum and heat transfer in a compressible boundary layerbehind a thin expansion wave was solved by the application of the similarity transformation and theshooting technique. Utilizing the analytical...The problem of momentum and heat transfer in a compressible boundary layerbehind a thin expansion wave was solved by the application of the similarity transformation and theshooting technique. Utilizing the analytical expression of a two-point boundary value problem formomentum transfer, the energy boundary layer solution was represented as a function of thedimensionless velocity, and as the parameters of the Prandtl number, the velocity ratio, and thetemperature ratio.展开更多
A second order heat equation with convection in an infinite medium isstudied. Suitable similarity transformations are used to reduce the parabolic heat equation to aClass of singular nonlinear boundary value problems....A second order heat equation with convection in an infinite medium isstudied. Suitable similarity transformations are used to reduce the parabolic heat equation to aClass of singular nonlinear boundary value problems. Numerical solutions are presented for differentrepresehtations of heat conduction, heat convection, heat flux, and power law parameters byutilizing the shooting technique. The results reveal the heat transfer characteristic and the effectof parameters on the solutions.展开更多
An algorithm for computing the 3-D oscillating flow field of the blade passage under the torsional vibra-tion of the rotor is applied to analyze the stability in turbomachines. The induced fiow field responding to bla...An algorithm for computing the 3-D oscillating flow field of the blade passage under the torsional vibra-tion of the rotor is applied to analyze the stability in turbomachines. The induced fiow field responding to blade vibration is computed by Oscillating Fluid Mechanics Method and ParaInetric Polynomial Method. After getting the solution of the unsteady flow field, the work done by the unsteay aerody natnic force acting on the blade can be obtained. The negative or positive work is the criterion of the aeroelastic stability Numerical results indicate that there are instabilities of the torsional vibration in some boency bands.展开更多
Experiments were conducted to investigate the heat transfer characteristics and cooling performance of subcooled liquid, water, flowing through rectangular cross-section microchanneled structures machined on a stainle...Experiments were conducted to investigate the heat transfer characteristics and cooling performance of subcooled liquid, water, flowing through rectangular cross-section microchanneled structures machined on a stainless steel plate. Heat transfer or flow mode transition was observed when the heating rate or wall temperature was increased. This transition was found to be suggestively induced by the variation in liquid thermophysical properties due to the significant rise of liquid temperature in the microstructures. The influence of such parameters as liquid velocity, subcooling, property variation, and microchannel geometric configuration on the heat transfer behavior, cooling performance and the heat transfer and liquid flow mode transition were also investigated. The experiments indicated that both slngle-phase forced convection and flow boiling characteristics were quite different from those in normal-sized tubes and the heat transfer was obviously intensified.展开更多
Experiments were conducted to investigate the single phase forced-flow convection of methanol flowing through microchannels with rectangular cross-section.The fully-developed turbulent convection regime was found to b...Experiments were conducted to investigate the single phase forced-flow convection of methanol flowing through microchannels with rectangular cross-section.The fully-developed turbulent convection regime was found to be initiated at about Re=1000-1500,The fully developed turbulent heat transfer can be predicted by the well-known Dittus-Boelter correlation with mere modification of the original empirical constant coefficient 0.023 to 0.00805.The transition and laminar heat transfer behaviors in microchannels are highly peculiar and complicated,and heavily affected by liquid temperature,velocity and microchannel size.展开更多
The characteristics of a vapor bubble within the thermal boundary layer were theoretically analyzed.The physical models accounting for the variation of ioterfacial tension and nuid density with tempera-ture were propo...The characteristics of a vapor bubble within the thermal boundary layer were theoretically analyzed.The physical models accounting for the variation of ioterfacial tension and nuid density with tempera-ture were proposed to investigate bubble interfaCe aspects and the fluid flow around the bubble. The analyses demonstrated that the variation in interfacial tension results in variations in the liquid-vapor interface shape and bubble dynamics, which may play a significant role in the departure process of a vapor bubble from a heated wall surface. Increasing temperature gradients in the boundary layer and the gravitational field induce a contact line contraction and correspondingly promotes bubble depar-ture. The simulation of liquid now around the bubble shows that natural convection dominates the flow for earth conditions; however, the thermocapillary forces provide the principal catalyst for bubble departure in a microgravity environment. The results indicate that both the vapor bubble contraction and the Marangoni flow may increase the heat transfer around the vapor bubble and may cause the bubble to mov away from the heating surface, further increasing heat transfer.展开更多
An theoretical investigation was conducted to detect the gas-solid interface effect on laminar flow characteristics for gas flowing through micropassages. In the wall-adjacent region, the change in viscosity of fluid ...An theoretical investigation was conducted to detect the gas-solid interface effect on laminar flow characteristics for gas flowing through micropassages. In the wall-adjacent region, the change in viscosity of fluid vs the distance from the wall surface, as derived from the kinetic theory of gases result in significallt influence on the flow characteristics in micropassages. A model was proposed to account for the wall effect. Analytical expressions for velocity profiles and pressure drop were derived, respectively,for laminar fiow of gases in microtubes and in extremely narrow parallel plates. The Knudsen number,Kn, as a criterion, that the fiow can be treated reasonably as flow in macrochannels, is discussed.展开更多
As part of the study on thermophysical properties of HFC-134a,this paper concerns itself with vapor pressure of HFC-134a in the temperature range of 279.15K to 365.15K.A total of 43 measurement data were measured duri...As part of the study on thermophysical properties of HFC-134a,this paper concerns itself with vapor pressure of HFC-134a in the temperature range of 279.15K to 365.15K.A total of 43 measurement data were measured during the experiment which was conducted on a high precision PVTx test apparatus designed by the authors with slight modifications.Uncertainties of temperature was ±10mK and of pressure was ±500Pa.Purity of sample was either 99.95wt% or 99.98wt%.Data resulting from this experiment matched closely with the newest data published internationally.Compared to our proposed equation for calculating vapor pressure of HFC-134a, the RMS deviation of experimental data was only 0.0531%,showing relatively high precision.展开更多
A fast and accurate numerical method for solving the two dimensional Reynolds aveaged Navier Stokes is applied to calculate the internal fluid of turbines and compressors. The code is based onan explicit, time-marchin...A fast and accurate numerical method for solving the two dimensional Reynolds aveaged Navier Stokes is applied to calculate the internal fluid of turbines and compressors. The code is based onan explicit, time-marching, finite volume technique. In order to accelerate convergence, local time stepping, multigrid method is employed. Four stage Runge-Kutta method is implemented to extend the stability domain. Test cases of Hobson’s impulse cascade, NASA Rotor 37 and Sanz’s supercritical compressor cascade are presented. Results of Mach number distribution on blade surfaces and Mach number contour plots indicate good agreement with experimental data. Compared with full three 3D Navier-Stokes (N-S) codes, the two dimensional code only takes a short time to obtain predicted results. This code can be used widely in practical engineering design.展开更多
To make it possible for the thermal wave theory on temperature oscillation (TO) effects in living tissues to be founded on the substantial experimental basis, a series of typical decisive experiments in vivo as well a...To make it possible for the thermal wave theory on temperature oscillation (TO) effects in living tissues to be founded on the substantial experimental basis, a series of typical decisive experiments in vivo as well as in artificially simulating constructions were carried out. Conclusions obtained including some other scholars' animal experimental results all greatly support the thermal wave viewpoint qualitatively.A few experimental facts used hot to be easily understood from the classical viewpoint are also well reinterpreted. The revealing on the thermal wave mechanisms of TO in living tissues is a brand new discovery and deep insight into this important thermophysiological phenomenon. It may possibly promote new investigations on the corresponding topics in the field of bioheat transfer science.展开更多
A theoretical investigation was conducted to study the transport-reaction process in the spray-drying flue gas desulfurization. A transport-reaction model of single particle was proposed, which considered the water ev...A theoretical investigation was conducted to study the transport-reaction process in the spray-drying flue gas desulfurization. A transport-reaction model of single particle was proposed, which considered the water evaporation from the surface of droplet and the reaction at the same time. Based on this model, the reaction rate and the absorbent utilization can be calculated. The most appropriate particle radius and the initial absorbent concentration can be deduced through comparing the wet lifetime with the residence time, the result shows in the case that the partial pressure of vapor in the bulk flue gas is 2000Pa, the optimum initial radius and absorbent concentration are 210～310 μ m and 23% respectively. The model can supply the optimum parameters for semi-dry FGD system designed.展开更多
基金[This work was financially supported by "973" key foundation of China (No.G 1998061510).]
文摘The skin friction and heat transfer occurring in the laminar boundary layerwhich caused by a vertical liquid jet impinging on a continuously moving horizontal plate werestudied. Similarity solutions for shear stress and heat distribution were obtained by using thehooting technique. The results show that the skin friction decreases with an increase of velocityparameter, the evolving of thermal boundary decrease with increasing in Prandtl number, but increasewith increasing of velocity parameter.
基金This work was supported by the "Cross-Century Talents Projects of the Educational Ministry of China"the "Projects of Investigations of Post Graduate School, University of Science and Technology Beijing".
文摘The problem of momentum and heat transfer in a compressible boundary layerbehind a thin expansion wave was solved by the application of the similarity transformation and theshooting technique. Utilizing the analytical expression of a two-point boundary value problem formomentum transfer, the energy boundary layer solution was represented as a function of thedimensionless velocity, and as the parameters of the Prandtl number, the velocity ratio, and thetemperature ratio.
基金This work was supported by Cross-Century Talents Projects of Educational Ministry of China the "973" Key Foundation under the contract No.G1998061510.]
文摘A second order heat equation with convection in an infinite medium isstudied. Suitable similarity transformations are used to reduce the parabolic heat equation to aClass of singular nonlinear boundary value problems. Numerical solutions are presented for differentrepresehtations of heat conduction, heat convection, heat flux, and power law parameters byutilizing the shooting technique. The results reveal the heat transfer characteristic and the effectof parameters on the solutions.
文摘An algorithm for computing the 3-D oscillating flow field of the blade passage under the torsional vibra-tion of the rotor is applied to analyze the stability in turbomachines. The induced fiow field responding to blade vibration is computed by Oscillating Fluid Mechanics Method and ParaInetric Polynomial Method. After getting the solution of the unsteady flow field, the work done by the unsteay aerody natnic force acting on the blade can be obtained. The negative or positive work is the criterion of the aeroelastic stability Numerical results indicate that there are instabilities of the torsional vibration in some boency bands.
基金This project is finmanced by the National Natural Science Foundation of China.
文摘Experiments were conducted to investigate the heat transfer characteristics and cooling performance of subcooled liquid, water, flowing through rectangular cross-section microchanneled structures machined on a stainless steel plate. Heat transfer or flow mode transition was observed when the heating rate or wall temperature was increased. This transition was found to be suggestively induced by the variation in liquid thermophysical properties due to the significant rise of liquid temperature in the microstructures. The influence of such parameters as liquid velocity, subcooling, property variation, and microchannel geometric configuration on the heat transfer behavior, cooling performance and the heat transfer and liquid flow mode transition were also investigated. The experiments indicated that both slngle-phase forced convection and flow boiling characteristics were quite different from those in normal-sized tubes and the heat transfer was obviously intensified.
文摘Experiments were conducted to investigate the single phase forced-flow convection of methanol flowing through microchannels with rectangular cross-section.The fully-developed turbulent convection regime was found to be initiated at about Re=1000-1500,The fully developed turbulent heat transfer can be predicted by the well-known Dittus-Boelter correlation with mere modification of the original empirical constant coefficient 0.023 to 0.00805.The transition and laminar heat transfer behaviors in microchannels are highly peculiar and complicated,and heavily affected by liquid temperature,velocity and microchannel size.
文摘The characteristics of a vapor bubble within the thermal boundary layer were theoretically analyzed.The physical models accounting for the variation of ioterfacial tension and nuid density with tempera-ture were proposed to investigate bubble interfaCe aspects and the fluid flow around the bubble. The analyses demonstrated that the variation in interfacial tension results in variations in the liquid-vapor interface shape and bubble dynamics, which may play a significant role in the departure process of a vapor bubble from a heated wall surface. Increasing temperature gradients in the boundary layer and the gravitational field induce a contact line contraction and correspondingly promotes bubble depar-ture. The simulation of liquid now around the bubble shows that natural convection dominates the flow for earth conditions; however, the thermocapillary forces provide the principal catalyst for bubble departure in a microgravity environment. The results indicate that both the vapor bubble contraction and the Marangoni flow may increase the heat transfer around the vapor bubble and may cause the bubble to mov away from the heating surface, further increasing heat transfer.
文摘An theoretical investigation was conducted to detect the gas-solid interface effect on laminar flow characteristics for gas flowing through micropassages. In the wall-adjacent region, the change in viscosity of fluid vs the distance from the wall surface, as derived from the kinetic theory of gases result in significallt influence on the flow characteristics in micropassages. A model was proposed to account for the wall effect. Analytical expressions for velocity profiles and pressure drop were derived, respectively,for laminar fiow of gases in microtubes and in extremely narrow parallel plates. The Knudsen number,Kn, as a criterion, that the fiow can be treated reasonably as flow in macrochannels, is discussed.
文摘As part of the study on thermophysical properties of HFC-134a,this paper concerns itself with vapor pressure of HFC-134a in the temperature range of 279.15K to 365.15K.A total of 43 measurement data were measured during the experiment which was conducted on a high precision PVTx test apparatus designed by the authors with slight modifications.Uncertainties of temperature was ±10mK and of pressure was ±500Pa.Purity of sample was either 99.95wt% or 99.98wt%.Data resulting from this experiment matched closely with the newest data published internationally.Compared to our proposed equation for calculating vapor pressure of HFC-134a, the RMS deviation of experimental data was only 0.0531%,showing relatively high precision.
文摘A fast and accurate numerical method for solving the two dimensional Reynolds aveaged Navier Stokes is applied to calculate the internal fluid of turbines and compressors. The code is based onan explicit, time-marching, finite volume technique. In order to accelerate convergence, local time stepping, multigrid method is employed. Four stage Runge-Kutta method is implemented to extend the stability domain. Test cases of Hobson’s impulse cascade, NASA Rotor 37 and Sanz’s supercritical compressor cascade are presented. Results of Mach number distribution on blade surfaces and Mach number contour plots indicate good agreement with experimental data. Compared with full three 3D Navier-Stokes (N-S) codes, the two dimensional code only takes a short time to obtain predicted results. This code can be used widely in practical engineering design.
文摘To make it possible for the thermal wave theory on temperature oscillation (TO) effects in living tissues to be founded on the substantial experimental basis, a series of typical decisive experiments in vivo as well as in artificially simulating constructions were carried out. Conclusions obtained including some other scholars' animal experimental results all greatly support the thermal wave viewpoint qualitatively.A few experimental facts used hot to be easily understood from the classical viewpoint are also well reinterpreted. The revealing on the thermal wave mechanisms of TO in living tissues is a brand new discovery and deep insight into this important thermophysiological phenomenon. It may possibly promote new investigations on the corresponding topics in the field of bioheat transfer science.
文摘A theoretical investigation was conducted to study the transport-reaction process in the spray-drying flue gas desulfurization. A transport-reaction model of single particle was proposed, which considered the water evaporation from the surface of droplet and the reaction at the same time. Based on this model, the reaction rate and the absorbent utilization can be calculated. The most appropriate particle radius and the initial absorbent concentration can be deduced through comparing the wet lifetime with the residence time, the result shows in the case that the partial pressure of vapor in the bulk flue gas is 2000Pa, the optimum initial radius and absorbent concentration are 210～310 μ m and 23% respectively. The model can supply the optimum parameters for semi-dry FGD system designed.
